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TLV342: Constant current driver regulated with digital potentiometer

Part Number: TLV342

Hello!

I am looking for working schematic ideas to build constant current pulse driver, for medical application. Pulses are delivered to a driver by MSP430 MCU, for example 200 usec 20 pulses per second. 

Driver is loaded with variable impedance loading, for example from 200 to 1000 Ohm. I need to have possibility to regulate pulse current in range 1...10 mA with resolution 0.5 mA or better.

I would like to implement this with combination of operational amplifier (like TLV342)  and digital potentiometer (like TPL0401 or TPL0501).

Digital potentiometer should have Non Volatile memory and have small outline, like 3x3 mm or smaller.

I have found one possible application example (for bipolar pulses), but it gives very low current, range microamperes:

Also I have tested another simple schematics of combination Op Amp + N-Mosfet - see below. It is working pretty good in my application, but I need add digital potentiometer to it.

The problem is, that value of current setting resistor should be something like from 360 to 1200 Ohm to have small mA output current range.

But in this case is hard to find low value digital potentiometer with small outline...

Could somebody recommend me schematics sample or any other ideas, where is possible to regulate output current (1-10 mA) with 10kOm (50k, 100k) digital potentiometer ?

  • Hi Vlad,

    The NMOS circuit you reference is a very common current sink circuit.  Could you source current instead of using a current sink? 

    Take a look at TIPD102.  It's a design that uses a standard topology for a two-stage current source where the first stage creates a current sink, using the circuit you've referenced, which is then mirrored and gained by the second stage which sources current into a ground referenced load.  Configure the first stage in the design with the digital potentiometer and then gain the current to the desired 0-10mA range using the second stage.  All required design equations are featured in the TIPD102 document. 

    Regards,
    Collin Wells
    General Purpose Amplifier Applications

  • In reply to Collin Wells:

    Dear Collin,

    Thanks a lot! It is really works according to TINA simulation. And article is very clear written, in 5 min I have received the required output parameters.

    I have been looked for such solution long time and now I'm very happy with good final result !!!

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